I secured mine down by screwing in the valley of the roofing, I bought the screws that have a neoprene washer to seal the water out, it's been on since March and has not leaked a drop I think the only way to use the top rib is if you buy the wavey piece of wood that fits under it, I think it's their way to sell you something to make them more money but I guess if you don't use them they probably won't cover any warranty issues.